Thomas Harvey Johnston (1881–1951)
Papers concerning prickly pear 1908-1937
T.H. Johnston, Professor of Zoology at the University of Adelaide from 1922 until his death in 1951, was closely associated with the campaign to eradicate prickly pear.
The common prickly pear was introduced to New South Wales as a potted plant in 1839. It was widely planted as hedges between paddocks in pastoral areas and was also used as fodder during drought. It spread rapidly until by 1920 an estimated 26 million hectares from Mackay to Newcastle were severely infested and farmers were forced to abandon their properties.
In 1912 Professor Johnston was appointed to the Queensland Prickly Pear Travelling Commission which was established to investigate how other nations were dealing with the spread of prickly pear and to decide on the most appropriate means of control in Queensland. The Commission found that the cost of chemical eradication was too great over such large areas and biological control was advocated.
The introduced cochineal insect Dactylopius ceylonicus controlled one species of the pear Opuntia monacantha. Johnston twice collected and introduced unsuccessfully the insect Cactoblastis cactorum in 1914, when it did feed on the pear but died out in 1921. The eventual devastation of the prickly pear followed a later introduction in 1924. The Prickly Pear Land Commission was established to study the results and to continue control of one of the most successful campaigns of biological control in Australia. Thousands of acres of previously infected land were restored to a condition suitable for development.
The Papers include reports of the Travelling Commission’s visits to Sydney, Java, Ceylon, Europe, the USA, Mexico and South America; reports of the Prickly Pear Land Commission 1925-1932; and correspondence, maps, newspaper articles, photographs and water-colours.
The records were presented to the Dept of Entomology on the death of Professor Johnston. They were later returned to the Dept of Zoology and then in 1981 presented to the Barr Smith Library.